JP2009116960A - Optical pickup and optical information recording and reproduction device provided with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin type optical pickup which copes with four media of a BD, HD-DVD, DVD and CD securing properties of the BD, HD-DVD, and an optical information recording and reproduction device provided with the same. <P>SOLUTION: In the optical pickup, a first objective lens 113 and a second objective lens 207 are arranged in the tangential direction of an information recording medium and they are mounted on an objective lens drive unit 114, and the optical pickup includes an optical path change optical element 107 formed by an integrated type prism which has two internal reflection planes and in which these reflection planes are almost orthogonal. Further, the objective lens drive unit 114 includes a space where a first light beam which transmits the polarization separating optical element 104 and of which the optical path is changed by the optical path changing optical element 107 and a second light beam reflected by the polarization separating optical element 104 and reflected by a prism 203 can pass therethrough from different directions each other with regard to the tangential line direction of the information recording medium. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical pickup having a function of recording or reproducing an information signal on an optical information recording medium.

  In recent years, a blue-violet laser light source having a wavelength of 405 nm is used as an optical disk having a larger capacity than conventional CDs and DVDs, and the data protection layer has a thickness of about 0.1 mm BD (Blu-ray Disc) and data protection layer. A large-capacity optical disk having a different standard called HD DVD (High-Definition DVD) having a length of about 0.6 mm has been developed.

  At present, there is no movement to unify the standards of BD and HD DVD, and there is a situation where large capacity optical disks of both standards exist in the market. Under such circumstances, 4 media compatible optical pickups that are compatible with both BD and HD DVD standards and also compatible with conventional CDs and DVDs, as well as a thin 4 that can be mounted on laptop computers, space-saving desktop computers, etc. A media compatible optical pickup is required.

  Examples of the 4-media compatible optical pickup are described in Patent Document 1 and Patent Document 2. In Patent Document 1, “it includes an optical path switching unit that is provided so as to electrically switch the traveling direction of light and selectively advances light incident from the optical unit side out of the first and second objective lenses”. Are listed.

  Further, in Patent Document 2, “a lens assembly having an objective lens set for one of BD and HD DVD having different substrate thicknesses and a liquid crystal lens is provided, and the liquid crystal lens is turned on during BD recording / reproduction. The light beam is irradiated with a numerical aperture of 0.85, and the liquid crystal lens is turned off at the time of HD DVD recording / reproduction so that the light beam is irradiated with a numerical aperture of 0.65.

JP 2006-24351 A (page 16, FIG. 2, FIG. 5) JP 2007-26540 A (page 17, FIGS. 1 and 2)

  In the above Patent Document 1, since the BD and the HD DVD optical system almost pass through the common optical path, the adjustment of the other optical system cannot be performed when the assembly adjustment of the optical system of either the BD or the HD DVD is completed. It is difficult to secure characteristics. Further, in Patent Document 2, since the BD objective lens and the liquid crystal lens are arranged in a common holder, the height dimension becomes large, and it is difficult to cope with a thin optical pickup that can be mounted on a slim type drive. .

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a thin optical pickup capable of supporting four media of BD, HD DVD, DVD, and CD and an optical information recording / reproducing apparatus equipped with the same. To do.

  The above object can be achieved by, for example, the configurations and means described in the claims.

  The following is a brief description of an outline of typical inventions disclosed in the present application.

  That is, in order to achieve the above object, an optical pickup of the present invention includes a laser light source that emits a linearly polarized light beam, a polarization direction conversion element that converts the polarization direction of the light beam, and the polarization direction conversion element. A polarization separation optical element for separating the polarization of the emitted light beam, a first objective lens for condensing the light beam transmitted through the polarization separation optical element on the information recording surface of the information recording medium, and the polarization separation optical element A prism that reflects the light beam reflected from the prism, a second objective lens that focuses the light beam emitted from the prism on the information recording surface of the information recording medium, the first objective lens, and the second objective lens. An objective lens driving unit for holding the lens so as to be aligned in the tangential direction of the information recording medium and driving the first objective lens and the second objective lens in a predetermined direction. And an optical path changing optical element provided so as to form an angle of approximately 90 degrees with each other. The first light beam that has been transmitted and whose optical path has been changed by the optical path changing optical element and the second light beam that has been reflected by the polarization separation optical element and reflected by the prism are mutually connected with respect to the tangential direction of the information recording medium. Spaces that can be passed from different directions are formed in the objective lens driving unit.

  According to the present invention, it is possible to provide a thin optical pickup compatible with four types of optical information recording media of BD, HD DVD, DVD, and CD, and an optical information recording / reproducing apparatus equipped with the same.

  Embodiments of a thin optical pickup and an optical information recording / reproducing apparatus corresponding to four types of optical information recording media of BD, HD DVD, DVD, and CD according to the present invention will be described below. However, the corresponding media are not limited to the above four types, and may be, for example, BD, DVD, CD or BD, DVD.

  A first embodiment of the optical pickup of the present invention will be described with reference to FIGS.

  First, the BD optical system will be described with reference to FIGS. 1, 3, and 6. 1 and 2 are simplified views for easy understanding of the optical pickup according to the present invention. (A) is a view seen from above, and (B) and (C) are views seen from the side. . 6A and 6B show the details of the BD optical system and the optical pickup added with the portions not described in FIGS. 1 and 2, (A) as viewed from above, and (B) and (C) as viewed from the side. The figure is shown.

  First, the BD optical system will be described with reference to FIGS. 1, 3, and 6. In FIG. 1, the X direction indicates the tangential direction of the information recording medium (BD), and the Y direction indicates the radial direction of the information recording medium (BD). The + Y direction corresponds to the inner peripheral side of the information recording medium (BD), and the −Y direction corresponds to the outer peripheral side. Reference numeral 101 denotes a pickup case in which optical system parts and mechanism parts of the optical pickup of this embodiment are mounted.

  A divergent light beam of linearly polarized light (P-polarized light) whose polarization direction is mostly ± Y direction in the wavelength λ1 = 405 nm band is emitted from the blue-violet laser light source 102, which is the first laser light source, and is incident on the polarization direction conversion element 103. . The polarization direction conversion element 103 is composed of, for example, a liquid crystal element in which liquid crystal is sandwiched between plate glasses and provided with a transparent electrode, and has the following two functions.

  (1) When a predetermined control voltage is applied from a drive circuit (not shown), the direction of linearly polarized light of the incident light beam is changed from ± Y direction (P-polarized light) to ± Z direction (S-polarized light) orthogonal to the ± Y direction. To do.

  (2) When a control voltage is not applied from a drive circuit (not shown), the incident light beam is transmitted as it is without changing the direction of the linearly polarized light.

  In the BD optical system of the present embodiment, no control voltage is applied to the polarization direction conversion element 103. Therefore, the divergent light beam is emitted from the polarization direction conversion element 103 while being linearly polarized light (P-polarized light) in the ± Y directions, and enters the polarization direction separation element 104. The polarization direction separation element 104 has a function of almost totally transmitting a linearly polarized light beam (P-polarized light) in the ± Y direction and substantially totally reflecting a light beam in the ± Z direction (S-polarized light) orthogonal to the ± Y direction. .

  The ± Y-direction linearly polarized (P-polarized) divergent light beam that has been almost completely transmitted through the polarization direction separation element 104 is converted into a parallel light beam by the first collimator lens 106 and enters the polarizing grating 601 (FIG. 6). reference). The polarizing grating 601 has a function of transmitting a linearly polarized light (P-polarized) light beam in the ± Y direction without diffracting, and diffracting a light beam in the ± Z direction (S-polarized light) and branching it into a plurality of light beams. Since the parallel light beam is linearly polarized light (P-polarized light) in the ± Y direction, it passes through the polarizing grating 601 without being diffracted.

  Next, the beam expander element formed by a pair of a concave lens 602 and a convex lens 603 is converted into a parallel light beam whose beam diameter is enlarged by about 1.1 to 1.5 times and is emitted from the convex lens 603. A diffraction groove (annular zone) is formed on the exit surface of the convex lens 603 in order to cancel chromatic aberration of the first objective lens 113 described later.

  The beam expander element has a function of translating the concave lens 602 from the reference position in the left-right direction of the optical path 105 by the expander driving mechanism 604 to change the light beam emitted from the convex lens 603 from parallel light to weakly divergent light or weakly convergent light. have. This beam expander element cancels the spherical aberration caused by the thickness error of the data protection layer of the information recording medium (BD), and the light spot on the information recording surface of the information recording medium (BD) is kept in the best state. Here, the best state means a state where the light spot diameter is minimum or the wavefront aberration of the light spot is minimum.

  As the expander driving mechanism 604, for example, a mechanism using a stepping motor and an optical sensor for detecting the position of the concave lens 602, or a mechanism using a piezoelectric element and a Hall element sensor for detecting the position of the concave lens 602, etc. It is possible to use. The expander drive mechanism 604 is electrically connected to an FPC (not shown), and this FPC is electrically connected to an expander drive circuit (not shown). The expander drive mechanism 604 is disposed on the outermost peripheral side in the pickup case 101.

  The parallel light beam emitted from the convex lens 603 enters the optical path changing optical element 107. The optical path changing optical element 107 is formed of a trapezoidal integral prism, has two internal reflection surfaces 108 and 110, and is formed so as to be substantially orthogonal. Further, it is arranged in the Y direction, that is, in the radial direction (Y direction) of the information recording medium (BD). The parallel light beam emitted from the convex lens 603 is bent 90 degrees from the optical path 105 to the optical path 109 by the internal reflection surface 108. Further, the optical path 109 is bent 90 degrees into the optical path 111 by the internal reflection surface 110. That is, the optical path of the parallel light beam emitted from the convex lens 603 by the optical path changing optical element 107 is changed from the optical path 105 to the optical path 111 by 180 degrees. The parallel light beam reflected by the internal reflection surface 110 is converted into circularly polarized light by the quarter wavelength plate 605, travels from the right to the left of the optical path 111, and passes through the objective lens driving unit 114.

  Here, the structure around the objective lens driving unit 114 will be described with reference to FIG. FIG. 3A is a view seen from above, and FIG. 3B is a cross-sectional view along X1-X1.

  3A, a first objective lens 113 and a second objective lens 207, which will be described later, are arranged side by side in the X direction, that is, the tangential direction of the information recording medium, and are mounted on a common holder 301. In order to reduce the size of the objective lens driving unit 114, the distance in the X direction between the center of the first objective lens 113 and the center of the second objective lens 207 is set as small as possible. In this embodiment, the distance is set to about 4 mm. Yes.

  The holder 301 is provided with a focus drive coil, tracking drive coil, and tilt drive coil (not shown). The holder 301 is coupled to the substrate 304 and the suspension holder 302 via a plurality of suspensions 303 (for example, a circular straight straight wire having a cross section of about 0.05 to 0.1 mm in diameter). The suspension 303 is fixed to the substrate 304 by soldering, and the substrate 304 is electrically connected to an FPC (not shown), and this FPC is electrically connected to an objective lens drive unit drive circuit (not shown).

  The plurality of magnets 305 are disposed to face the holder 301 and are fixed to the yoke 306. The first objective lens 113 and the second objective lens 207 are translationally driven (focus operation) in the ± Z directions in the figure by energizing a focus drive coil (not shown). Further, when a tracking drive coil (not shown) is energized, translational driving (tracking operation) is performed in the ± Y direction in the figure, and when a tilt drive coil (not shown) is energized, rotation driving (tilt operation) is performed around the X axis in the figure.

  As shown in FIG. 3 (B), the parallel light beam 309 reflected by the internal reflection surface 110 of the optical path changing optical element 107 is applied to the suspension holder 302, the substrate 304, and the yoke 306 in the −X direction in FIG. Light beam passage spaces 310, 311, and 312 that can pass in the tangential direction of the medium are provided. The yoke 306 is provided with a light beam passage space 308 which will be described later. With this structure, the performance of the objective lens driving unit 114 can be ensured without affecting the arrangement of the holder 301, the plurality of suspensions 303, and the plurality of magnets 305. Further, since the light beam passage spaces 310, 311, 312, and 308 are provided in this way, it is not necessary to lift the objective lens driving unit 114 above (in the + Z direction) the parallel light beam 309. There is an effect that the pickup can be thinned.

  The parallel light beam 309 that has passed through the light beam passage spaces 310 and 311 has its optical path bent in the + Z direction in the figure by the rising mirror 112, is incident on the first objective lens 113, is condensed, and is recorded on the information recording medium (BD ) Is irradiated with a light spot. Here, the first objective lens 113 is a BD objective lens, and is formed of a single glass lens having a numerical aperture of 0.85.

  The light beam reflected by the track on the information recording surface passes through the first objective lens 113 to become a parallel light beam, is reflected by the rising mirror 112, and passes through the light beam passage spaces 312, 311, and 310 in the + X direction in the figure. pass. This parallel light beam is converted into linearly polarized light (S-polarized light) in the ± Z direction by the ¼ wavelength plate 605 and is incident on the optical path changing optical element 107.

  Hereinafter, description will be made with reference back to FIGS. In FIG. 1, the optical path 111 of the parallel light beam incident on the optical path changing optical element 107 is bent by 180 degrees by the internal reflection surfaces 110 and 108 to be changed to the optical path 105, and from right to left (−X direction). proceed. Thereafter, a parallel light beam that is transmitted through the convex lens 603 and the concave lens 602 of the beam expander element and whose beam diameter is reduced is incident on the multi-dividing polarizing grating 601. Since the parallel light beam is linearly polarized light (S-polarized light) in the ± Z direction, it is diffracted into ± first-order light by the grating plane of the multi-partition polarizing grating 601 and branched into a plurality of light beams. The spectral ratio between the + 1st order light and the −1st order light is arbitrarily set as necessary.

  Further, the light passes through the first collimating lens 106 to become convergent light, is reflected almost 100% by the polarization direction separation element 104, is changed to an optical path 116, and enters the BD photodetector 117. The BD photodetector 117 is provided with a plurality of light detection surfaces for receiving a plurality of light beams branched. The plurality of light detection surfaces include a focus error signal detection surface, a tracking error signal detection surface, and an information signal (RF) detection surface, and the focus error signal detection surface and the tracking error signal detection surface are provided separately.

  The BD optical system of this embodiment is a one-beam system. As a servo signal detection system, a double knife edge method or spot size method (SSD) is used for detecting a focus error signal, and a push-pull method is used for detecting a tracking error signal. It is possible to use the DPD method. In addition, since these detection methods are well-known techniques, description is abbreviate | omitted here.

  In BD, there is a two-layer medium having an information recording surface of L0 layer and L1 layer (layer spacing of about 25 μm). In this embodiment, unnecessary light reflected from the L1 layer when the L0 layer is reproduced or unnecessary light reflected from the L0 layer when the L1 layer is reproduced is detected on the tracking error signal detection surface of the BD photodetector 117. It is configured to prevent the incident and to detect the tracking error signal stably. As described above, the grating division shape, the grating pitch, the grating angle, and the tracking error signal detection surface of the BD photodetector 117 are set.

  Further, although the BD optical system of the present embodiment is a one-beam system, the axis line connecting the rotation center of the information recording medium (BD) (not shown) and the center of the first objective lens 113 is relative to the Y direction in FIG. It is configured to have an inclination rather than parallel. Therefore, the angle formed between the light spot on the information recording surface on the information recording medium (BD) and the tangential direction of the track in the innermost circumference (+ Y direction) of the information recording medium (BD) is more than in the outermost circumference (−Y direction). Is big. Therefore, the push-pull pattern (pattern in which 0th-order light and ± 1st-order diffracted light overlap) diffracted at the time of reflection at the track on the information recording surface of the information recording medium (BD) depends on the radial position of the information recording medium (BD). It rotates about the axis of the optical path 105 on the grating surface of the multi-partition polarizing grating 601, and the rotation angle of the innermost circumference of the information recording medium (BD) is larger than that of the outermost circumference. As a result, a large difference occurs in the signal amplitude detected by the push-pull method between the innermost periphery and the outermost periphery. In other words, the signal amplitude of the tracking error signal varies depending on the radial position of the information recording medium (BD), which adversely affects the tracking servo.

  Therefore, in this embodiment, the signal amplitude detected by the push-pull method is averaged at the radial position of the information recording medium (BD) to suppress fluctuations, so that the grating surface of the polarizing grating 601 is rotated around the axis of the optical path 105. The polarizing grating 601 is arranged by rotating about 7 degrees. Further, although not shown, it is possible to dispose, for example, a cylindrical lens-shaped beam shaping element formed of two cylindrical surfaces between the blue-violet laser 102 and the polarization direction conversion element 103. In this case, since the light use efficiency of the BD optical system is improved, it is possible to improve the BD recording speed.

  Next, the HD DVD optical system will be described with reference to FIG. 2, FIG. 3, and FIG. 2A and 2B are simplified views for easy understanding of the present invention. FIG. 2A is a view seen from above, and FIGS. 2B and 2C are views seen from the side. 6A and 6B show the details of the HD DVD optical system and the optical pickup to which a portion not described in FIG. 2 is added. FIG. 6A is a view seen from above, and FIGS. Show.

  In FIG. 2, the X direction indicates the tangential direction of the information recording medium (HD DVD), and the Y direction indicates the radial direction of the information recording medium (HD DVD). The + Y direction corresponds to the inner circumference side of the information recording medium (HD DVD), and the −Y direction corresponds to the outer circumference side.

  A divergent light beam of linearly polarized light (P-polarized light) whose polarization direction is mostly ± Y direction in the wavelength λ1 = 405 nm band is emitted from the blue-violet laser light source 102, which is the first laser light source, and is incident on the polarization direction conversion element 103. . In the HD DVD optical system of the present embodiment, a predetermined control voltage is applied to the polarization direction conversion element 103, and the linear polarization direction of the diverging light beam incident on the polarization direction conversion element 103 is ± Z direction (S Converted into polarized light) and emitted from the polarization direction conversion element 103. Although this outgoing diverging light beam is incident on the polarization direction separation element 104, the linearly polarized light direction is the ± Z direction (S-polarized light), so that it is almost totally reflected and the optical path is changed to 201.

  Next, the divergence state is changed by passing through the HD auxiliary lens 202 (approaching the parallel light), and is branched into one main light beam and two sub light beams by the HD diffraction grating 611, and the second three-wavelength prism In 203, the light is totally reflected and the optical path is changed to 204. Here, the three-wavelength prism is a prism corresponding to any light having different wavelengths of HD DVD light, DVD light, and CD light. The polarization direction separation element 104 and the second three-wavelength prism 203 are arranged side by side in the Y direction in the drawing, that is, in the radial direction of the information recording medium, and the polarization direction separation element 104 is closer to the information recording medium than the second three-wavelength prism 203. It arrange | positions at the outer peripheral side (-Y direction).

  Next, the divergent light beam passes through the second collimating lens 205 and is converted into a parallel light beam. The parallel light beam emitted from the second collimating lens 205 enters the three-wavelength liquid crystal aberration correction element 608, is converted into circularly polarized light by the three-wavelength quarter-wave plate 609, and proceeds from the left to the right of the optical path 204. It passes through the objective lens driving unit 114. Here, the three-wavelength liquid crystal aberration correction element is a liquid crystal aberration correction element corresponding to any of HD DVD light, DVD light, and CD light. In addition, the three-wavelength quarter-wave plate 609 is an element that functions as a quarter-wave plate for any light having different wavelengths such as HD DVD light, DVD light, and CD light.

  As shown in FIG. 3B, the parallel light beam 307 emitted from the second collimating lens 205 can pass through the yoke 306 of the objective lens driving unit 114 in the + X direction of the drawing, that is, the tangential direction of the information recording medium. A light beam passage space 308 is provided. The parallel light beam 307 that has passed through the light beam passage space 308 has its optical path bent in the + Z direction in the figure by the three-wavelength raising mirror 206, is incident on the second objective lens 207, is condensed, and is recorded on the information recording medium ( A light spot is irradiated onto a track on the information recording surface of HD DVD. Here, the three-wavelength raising mirror 206 is an element having a function of substantially totally reflecting any of HD DVD light, DVD light, and CD light having different wavelengths.

  The second objective lens 207 is an HD DVD, DVD, or CD compatible objective lens, and is formed of a single plastic lens. A diffraction groove is provided on the incident surface to realize compatibility. In the case of HD DVD, the numerical aperture is set to about 0.65 to 0.67. In this embodiment, the optical magnification of the HD DVD optical system (the combined focal length of the HD auxiliary lens 202 and the second collimating lens 205 / the HD DVD focal length of the second objective lens 207) is about 7 times.

  Here, in this embodiment, two objective lenses, a first objective lens 113 (BD dedicated lens) and a second objective lens 207 (HD DVD, DVD, CD compatible objective lens) are mounted on the holder 301. However, an attachment angle error relative to the second objective lens 207 with respect to the first objective lens 113 may occur. Therefore, in the second objective lens 207, the angle with respect to the information recording medium is deviated from the optimum angle in the radial direction and the tangential direction of the information recording medium. In order to correct this angle to the optimum angle, a three-wavelength liquid crystal aberration correction element 608 is provided between the second collimating lens 205 and the second objective lens 207.

  Since the angular error between the radial direction and the tangential direction with respect to the information recording medium corresponds to coma aberration, the three-wavelength liquid crystal aberration correction element 608 has a function of correcting coma aberration generated in two directions of the information recording medium in the radial direction and the tangential direction. Have. Among HD DVDs, DVDs, and CDs, HD DVD has the smallest track pitch, mark length, and short wavelength so that it is the most severe in angular error, and the three-wavelength liquid crystal aberration is best corrected for coma at wavelength λ1 = 405 nm. An electrode pattern of the correction element 608 is set. Although the correction amount is different from that of HD DVD, the electrode pattern of the three-wavelength liquid crystal aberration correction element 608 is set so that coma generated in two directions of the radial direction and the tangential direction is also corrected for DVD and CD. Has been.

  In addition, although there are two-layer media having a two-layer information recording surface in HD DVD, development of three-layer media is expected in the future. A spherical aberration correction optical element (not shown) is added to the three-wavelength liquid crystal aberration correction element 608, or the coma aberration correction function in the radial direction of the information recording medium is deleted from the three-wavelength liquid crystal aberration correction element 608 (in this case, the objective lens drive Although the burden of tilting operation of the unit is slightly increased, it is not at a level that causes trouble), and by adding a spherical aberration correcting optical element, the spherical aberration of the light spot irradiated on the track of the information recording surface of the HD DVD is reduced. This has the effect of improving the quality of the light spot. As a result, it becomes possible to correspond to a medium in which the layer spacing error of the two-layer medium is larger than the standard or to a three-layer medium.

  The light beam reflected by the track on the information recording surface passes through the second objective lens 207 to become a parallel light beam, is reflected by the three-wavelength rising mirror 206, and passes through the light beam passage space 307 in the -X direction in the figure. To do.

  Hereinafter, description will be made with reference back to FIGS. This parallel light beam is converted into ± Y-direction linearly polarized light (P-polarized light) by a three-wavelength quarter-wave plate 609, transmitted through the three-wavelength liquid crystal aberration correction element 608, and transmitted through the second collimator lens 205 to converge. It becomes a light beam and enters the second three-wavelength prism 203. The convergent light beam passes through the second three-wavelength prism 203 and the first three-wavelength prism 209, passes through the detection lens 610, and is collected and incident on the HD DVD / DVD / CD photodetector 210. The detection lens 610 has a function of setting a desired amount of astigmatism, arbitrarily rotating the direction of astigmatism, and determining the size of the focused spot on the photodetector 210. In order to receive the three light beams, the light detector 210 has three light detection surfaces arranged in the ± Z direction (vertical direction). The light detection surface is divided into four regions in a square shape. In the HD DVD optical system of this embodiment, it is possible to use the astigmatism method or the differential astigmatism method for detecting the focus error signal and the DPP method or DPD method for detecting the tracking error signal as the servo signal detection method. It is. In addition, since these detection methods are well-known techniques, description is abbreviate | omitted here.

  Hereinafter, effects of the present embodiment will be described together. In this embodiment, a polarization direction conversion element for converting the polarization direction of the emitted light beam of the blue-violet laser light source, an optical path changing optical element having two internal reflection surfaces in order to change the BD optical path by 180 degrees, and BD are provided. The optical system and the HD DVD optical system have almost no common optical path, and are parallel and perpendicular optical paths. In addition, a space that allows both BD light and HD DVD light to pass through is provided in the structural parts that do not affect the performance of the objective lens drive unit, and BD light is directed from the -X direction and HD DVD light is directed to the + X direction. In other words, both light beams are incident on separate objective lenses from the tangential direction of the information recording medium, which are opposite to each other. Therefore, the following effects can be obtained.

(1) Optical design, mounting design, and pickup case design are relatively easy with the BD optical system and the HD DVD optical system, and an optimum optical design is possible with each optical system.
(2) Since the assembly adjustment of the BD optical system and the HD DVD optical system can be performed independently, an optical pickup with high productivity can be realized.
(3) Since the most expensive blue-violet laser light source can be used for both BD and HD DVD, it is possible to suppress the cost increase of the optical pickup.
(4) Since the objective lens driving unit and the optical system can be arranged planarly without increasing the dimension in the thickness direction, a thin optical pickup that can be mounted on a slim type drive can be realized.

  In this embodiment, the rising mirror 112 and the three-wavelength rising mirror 206 are formed as flat plates. However, the present invention is not limited to this. For example, as shown in FIG. 401 or the rising mirror 402 may be used. Alternatively, as shown in FIG. 4B, an integrated prism-shaped three-wavelength rising mirror 403 may be provided, and two reflecting surfaces 404 and 405 may be provided.

  In this embodiment, as the optical path changing optical element 109, a trapezoidal prism formed integrally and having two internal reflection surfaces is used. Then, a light beam is incident from the lower base surface of the trapezoid, reflected from the two reflecting surfaces inside the trapezoidal prism, and then from a position different from the position of the incident light beam on the lower base surface. A light beam is emitted. The light beam incident on the trapezoidal prism and the light beam emitted from the trapezoidal prism are parallel to each other and are different in direction by 180 degrees. Here, the term “parallel” is an ideal concept and includes a deviation caused by a design error of the prism.

  As this optical path changing optical element, for example, two triangular prisms 502 and 504 separated as shown in FIG. 5A may be provided, and internal reflection surfaces 501 and 503 may be provided. Alternatively, as shown in FIG. 5B, it may be possible to provide two flat reflection mirrors 505 and 506. However, since both have a structure in which the two reflecting surfaces are separated, the optical axis shift of the BD light incident on the first objective lens 113 is likely to occur at the time of assembly, and the optical axis adjustment accuracy deteriorates and the BD light is deteriorated. There is a drawback that the quality of the light spot on the recording surface of the information recording medium deteriorates. In that regard, when the optical path changing optical element 109 formed of the trapezoidal prism shown in FIG. 1 is used, the two reflecting surfaces are formed integrally and high component accuracy can be expected, so that the optical axis can be easily adjusted, and Since high optical axis adjustment accuracy can be achieved, the quality of the light spot on the information recording medium recording surface of the BD light can be increased. Further, since the optical path changing optical element 109 is made of glass, the optical path length of the BD optical system can be shortened.

  The optical path polarizing optical element 10 is not limited to the trapezoidal prism 107 shown in FIG. 1, and an incident light beam is reflected inside the element and is approximately 180 with respect to the incident light beam from a position different from the incident light beam. Any shape may be used as long as the optical element has a function of emitting light in the opposite direction. For example, a right-angle prism having two reflecting surfaces having an angle of 90 degrees with each other may be used as the optical path polarization optical element.

  Next, the DVD and CD optical systems will be described with reference to FIGS. 2A and 2B are simplified views for easy understanding of the present invention. FIG. 2A is a view seen from above, and FIGS. 2B and 2C are views seen from the side. 6A and 6B show the details of the DVD, CD optical system, and optical pickup added with parts not described in FIG. 2, (A) is a view from above, and (B) and (C) are views from the side. Indicates.

  In FIG. 2, reference numeral 208 denotes a two-wavelength multi-laser, which includes a DVD laser chip (not shown) that emits a light beam of wavelength λ2 = 660 nm and a CD laser chip (not shown) that emits a light beam of wavelength λ3 = 780 nm. It is installed. First, the DVD optical system will be described.

  From the DVD laser chip of the two-wavelength multi-laser 208, a linearly polarized (P-polarized) divergent light beam is emitted mostly in the ± X direction. When the diverging light beam is incident on the two-wavelength half-wave plate 606, it is converted into linearly polarized light (S-polarized light) in the ± Z direction orthogonal to the ± X direction and emitted. The two-wavelength half-wave plate 606 functions as a half-wave plate for both wavelengths when a DVD light beam having a wavelength λ2 = 660 nm band and a CD light beam having a wavelength λ3 = 780 nm band are incident. It is an element. The divergent light beam emitted from the two-wavelength half-wave plate 606 is incident on a DVD / CD diffraction grating 607, which is an element having a two-plate structure and wavelength selectivity.

  When a DVD light beam having a wavelength λ2 = 660 nm band is incident on the DVD / CD diffraction grating 607, the diffraction angle θ1 is obtained. When a CD light beam having a wavelength λ3 = 780 nm band is incident, one main beam is formed at a diffraction angle θ2 different from the diffraction angle θ1. The light beam and two sub light beams are branched. The divergent light beam emitted from the DVD / CD diffraction grating 607 is substantially totally reflected by the first three-wavelength prism 209, and the optical path is changed to 204. The light passes through the second three-wavelength prism 203 and is converted into a parallel light beam by the second collimating lens 205. The parallel light beam emitted from the second collimating lens 205 enters the three-wavelength liquid crystal aberration correction element 608.

  The three-wavelength liquid crystal aberration correction element 608 corrects coma aberration that occurs in two directions, the radial direction and the tangential direction of the information recording medium, even for DVD and CD light, although the correction amount is different from that of the HD DVD light already described. It has a function to do. The parallel light beam that has passed through the three-wavelength liquid crystal aberration correction element 608 is converted into circularly polarized light by the three-wavelength quarter-wave plate 609, travels from the left to the right of the optical path 204, and passes through the objective lens driving unit 114. .

  As shown in FIG. 3B, light that can pass through the parallel light beam emitted from the second collimator lens 205 in the yoke 306 of the objective lens driving unit 114 in the + X direction in the drawing, that is, the tangential direction of the information recording medium. A beam passage space 308 is provided. The parallel light beam that has passed through the light beam passage space 308 has its optical path bent in the + Z direction in the figure by the three-wavelength rising mirror 206, is incident on the second objective lens 207, is condensed, and is recorded on the information recording medium (DVD ) Is irradiated with a light spot.

  In the second objective lens 207, the numerical aperture is set to about 0.65 in the case of DVD. In this embodiment, the optical magnification of the DVD optical system (the focal length of the second collimating lens 205 / the DVD focal length of the second objective lens 207) is about 5 to 6 times. The light beam reflected by the track on the information recording surface passes through the second objective lens 207 to become a parallel light beam, is reflected by the three-wavelength rising mirror 206, and passes through the light beam passage space 307 in the -X direction in the figure. To do.

  Hereinafter, description will be made with reference back to FIGS. This parallel light beam is converted into ± Y-direction linearly polarized light (P-polarized light) by a three-wavelength quarter-wave plate 609, transmitted through the three-wavelength liquid crystal aberration correction element 608, and transmitted through the second collimator lens 205 to converge. It becomes a light beam and enters the second three-wavelength prism 203. The convergent light beam passes through the second three-wavelength prism 203 and the first three-wavelength prism 209, passes through the detection lens 610, and is collected and incident on the HD DVD / DVD / CD photodetector 210. In the DVD optical system of this embodiment, the photodetection surface for DVD is shared with the photodetection surface for HD DVD already described. Therefore, the same method as the HD DVD optical system can be used for the detection of the servo signal.

  Next, the CD optical system will be described. A divergent light beam in the wavelength λ3 = 780 nm band, which is mostly linearly polarized light (P-polarized light) in the ± X direction, is emitted from the CD laser chip of the two-wavelength multilaser 208. Thereafter, the light travels in substantially the same optical path as that of the DVD, enters the second objective lens 207 and is condensed, and the light spot is irradiated onto the track on the information recording surface of the information recording medium (CD). In the second objective lens 207, in the case of CD, the numerical aperture is set to about 0.51 to 0.53. In this embodiment, the optical magnification of the CD optical system (focal length of the second collimating lens 205 / CD focal length of the second objective lens 207) is substantially the same as that of DVD, and is about 5 to 6 times.

  The light beam reflected by the track on the information recording surface travels almost the same optical path as that of the DVD, passes through the detection lens 610, and is collected and incident on the HD DVD / DVD / CD photodetector 210. In order to receive the three light beams, the HD DVD / DVD / CD photodetector 210 has a rice-shaped photodetection surface in the ± Z direction (vertical direction) on the side of the photodetection surface for DVD (Y direction). ) Is provided with three photodetecting surfaces for CDs arranged side by side. This is because the CD emission point of the two-wavelength multi-laser 208 is about 110 μm away from the DVD emission point in the X direction (lateral direction). Although not shown in the present embodiment, a front monitor element for receiving a light beam emitted toward the front of the laser light source is provided. The light quantity of the emitted light beam is detected by the front monitor element, and the light quantity of the light beam applied to the information recording medium is controlled to a desired value by feeding back the detected light quantity to the control circuit of the laser light source.

  In this embodiment, the second collimating lens 205 is arranged in the common optical path of the HD DVD optical system and the DVD optical system, and the HD auxiliary lens 202 is arranged in the optical path of only the HD DVD optical system. That is, the second collimating lens 205 determines the optical magnification of the DVD and CD optical system, and the second collimating lens 205 and the HD auxiliary lens 202 determine the optical magnification of the HD DVD optical system. Therefore, there is an effect that an optimum optical magnification can be set in both the DVD, CD optical system and the HD DVD optical system. Further, since the HD DVD photodetection surface and the DVD photodetection surface are shared, there is an effect that the photodetection surface of the HD DVD / DVD / CD photodetector can be simplified.

  As described above, the embodiments of the optical pickup corresponding to the four types of optical information recording media of BD, HD DVD, DVD, and CD have been described, but the present invention is not limited to this.

  For example, as shown in FIG. 7, the polarization direction conversion element 103, the HD auxiliary lens 202, and the HD diffraction grating 611 are deleted from FIG. 6, and the three types of optical information of BD, DVD, and CD are used while the pickup case 101 is shared. It is possible to change to an optical pickup corresponding to the recording medium. (A) shows a case where 701 is arranged as a glass block made of the same material as that of the second three-wavelength prism 203, and (B) shows a case where 701 in (A) is deleted and the collimating lens 703 is replaced with the second one shown in FIG. The case where it changes from the collimating lens 205 is shown. In this case, it is possible to change the optical magnification of the DVD and CD optical system from FIG. 6, and there is an effect that the degree of freedom in optical design can be improved.

  Here, the optical pickup for BD, HD DVD, DVD, and CD when the first objective lens 113 and the second objective lens 207 are arranged side by side in the radial direction of the information recording medium without taking the form of the present embodiment. The problem of is explained. In this case, the second objective lens 207 and the first objective lens 113 are arranged side by side in the radial direction (Y direction) of the information recording medium. However, in order to reduce the size of the objective lens driving unit, It is necessary to set the center interval as small as possible. Further, the first objective lens 113 is arranged on the outer peripheral side of the information recording medium with respect to the second objective lens 207 (conversely, the objective lens 113 is placed on the inner peripheral side of the information recording medium with respect to the second objective lens 207. Therefore, in order to make the first objective lens 113 accessible to the outermost peripheral position of the information recording medium, the center of rotation of the information recording medium and the center of the second objective lens 207 are selected for the pickup case. The dimension in the axial direction connecting the centers of the first objective lenses 113 must be made smaller by the distance between the two objective lens centers than the pickup case 101 shown in FIGS. That is, the size of the pickup case in the radial direction of the information recording medium must be smaller than that of the pickup case 101. Therefore, the following problems occur.

(1) The optical system cannot be arranged unless both the optical path of the BD optical system and the optical path of the HD DVD, DVD, and CD optical systems are tilted. For this reason, optical design, mounting design, and pickup case design become difficult.
(2) The above (1) makes it difficult to adjust the assembly of the optical system.
(3) Due to the above (1), the polarization direction separation element and the three-wavelength prism must be specially shaped, which increases the cost of the optical pickup.
(4) According to the above (1), the movable BD collimating lens for correcting spherical aberration has to be disposed obliquely. Therefore, when the entire optical pickup performs a seek operation in the radial direction of the information recording medium, the movable BD is moved by inertial force. The position of the collimating lens tends to shift in the optical axis direction, and the spherical aberration correction performance is degraded.

  In the optical pickup of the present embodiment, the above problem does not occur due to the configuration, so that the configuration is superior to the case where the first objective lens 113 and the second objective lens 207 are arranged side by side in the radial direction of the information recording medium. It can be said.

  A second embodiment of the optical pickup of the present invention will be described with reference to FIGS. FIG. 8 shows a BD optical system, where (A) shows a view from above, and (B) and (C) show views from the side. Since the BD optical system is the same as that of the first embodiment, the description thereof is omitted here.

  Next, the HD DVD, DVD, and CD optical system will be described with reference to FIG. (A) shows the figure seen from the top, (B), (C) shows the figure seen from the side. The difference from the first embodiment is that the DVD hologram unit 905, which is the first hologram unit, and the CD hologram unit 907, which is the second hologram unit, are used for the DVD and CD optical systems. It is that we changed the part.

  First, the HD DVD optical system will be described. A divergent light beam of linearly polarized light (P-polarized light) whose polarization direction is mostly ± Y direction in the wavelength λ1 = 405 nm band is emitted from the blue-violet laser light source 102, which is the first laser light source, and is incident on the polarization direction conversion element 103. . In the HD DVD optical system of the present embodiment, a predetermined control voltage is applied to the polarization direction conversion element 103, and the linear polarization direction of the diverging light beam incident on the polarization direction conversion element 103 is ± Z direction (S Converted into polarized light) and emitted from the polarization direction conversion element 103. Although this outgoing diverging light beam is incident on the polarization direction separation element 104, the linearly polarized light direction is the ± Z direction (S-polarized light), so that it is almost totally reflected and the optical path is changed to 201.

  Next, the light is transmitted through the HD auxiliary lens 901, the divergence state is changed (approaches parallel light), and is incident on the HD multi-dividing polarizing grating 909. The HD multi-partition polarizing grating 909 transmits a linearly polarized light beam (S-polarized light) in the ± Z direction without diffracting it, diffracts the light beam in the ± Y direction (P-polarized light), and branches it into a plurality of light beams. Has function. Since the divergent light beam is linearly polarized light (S-polarized light) in the ± Z direction, it passes through the HD multi-partition polarizing grating 909 without being diffracted. Thereafter, the light is substantially totally reflected by the third three-wavelength prism 902, passes through the fourth collimating lens 903, and is converted into a parallel light beam.

  In the present embodiment, the third three-wavelength prism 902 almost totally reflects the light beam in the wavelength λ1 = 405 nm band regardless of the polarization direction, and the light beam in the wavelength λ2 = 660 nm band and the light beam in the wavelength λ3 = 780 nm band. Has a function of transmitting almost all of the light regardless of the polarization direction. In this embodiment, the optical magnification of the HD DVD optical system (the combined focal length / the HD DVD focal length of the second objective lens 207) is about 7 times.

  The parallel light beam emitted from the fourth collimator lens 903 enters the three-wavelength liquid crystal aberration correction element 608, is converted into circularly polarized light by the three-wavelength quarter-wave plate 609, and passes through the objective lens driving unit 114. Similar to the first embodiment, the parallel light beam 307 that has passed through the light beam passage space 308 has its optical path bent in the + Z direction in the figure by the three-wavelength rising mirror 206, and is incident on the second objective lens 207 to be condensed. Then, the light spot is irradiated onto the track on the information recording surface of the information recording medium (HD DVD).

  The light beam reflected by the track on the information recording surface passes through the second objective lens 207 and becomes a parallel light beam as in the first embodiment, and is reflected by the three-wavelength rising mirror 206 and passes through the light beam passage space 307. It passes in the -X direction in the figure. This parallel light beam is converted into ± Y-direction linearly polarized light (P-polarized light) by the three-wavelength quarter-wave plate 609, transmitted through the three-wavelength liquid crystal aberration correction element 608, and transmitted through the fourth collimator lens 903 to converge. It becomes a light beam and enters the third three-wavelength prism 902. This convergent light beam is substantially totally reflected by the third three-wavelength prism 902 and enters the HD multi-dividing polarizing grating 909. Since this convergent light beam is linearly polarized light (P-polarized light) in the ± Y direction, it is diffracted into ± first-order light by the grating surface of the HD multi-partition polarizing grating 909 and branched into a plurality of light beams. The spectral ratio between the + 1st order light and the −1st order light is arbitrarily set as necessary.

  Further, the light passes through the HD auxiliary lens 901 and the polarization direction separation element 104 almost completely, and enters the BD photodetector 117. That is, the photodetector is shared with the BD optical system. The HD polarizing grating 909 has the same division shape as the polarizing grating 601 described in the first embodiment, but has different dimensions because the incident light beam diameter on the grating surface is different from that of the BD optical system. Further, the grating pitch and grating angle of the HD multi-dividing polarizing grating 909 are set so that a plurality of light beams are incident at the same position as the plurality of light detection surfaces for BD. Since the photodetector is shared with the BD optical system, the servo signal detection method is the same as that of the BD optical system.

  The HD DVD optical system of this embodiment is a one-beam system, and the axis connecting the rotation center of an information recording medium (HD DVD) (not shown) and the center of the second objective lens 207 is parallel to the Y direction in FIG. It has no inclination. Therefore, the angle formed by the light spot on the information recording surface on the information recording medium and the tangential direction of the track is the same at the innermost circumference (+ Y direction) and the outermost circumference (−Y direction) of the information recording medium. Therefore, unlike the BD optical system, it is not necessary to rotate the grating surface of the HD multi-partition polarizing grating 909 around the optical axis.

  Next, the DVD optical system will be described. Reference numeral 905 denotes a DVD hologram unit which is a first hologram unit, and a linearly polarized divergent light beam (P-polarized light) having a wavelength λ2 = 660 nm band is emitted from a laser light emitting unit (not shown). Almost totally reflected. The dichroic prism 906 of this embodiment has a function of substantially totally reflecting DVD light with a wavelength λ2 = 660 nm band regardless of the polarization direction and almost totally transmitting CD light with a wavelength λ3 = 780 nm band regardless of the polarization direction. Thereafter, the light beam is substantially totally transmitted through the third three-wavelength prism 902 and transmitted through the fourth collimating lens 903 to be converted into a parallel light beam. In this embodiment, the optical magnification of the DVD optical system is set to about 5 to 6 times.

  Thereafter, the parallel light beam enters the three-wavelength liquid crystal aberration correction element 608, is converted into circularly polarized light by the three-wavelength quarter-wave plate 609, and passes through the objective lens driving unit 114. Similar to the first embodiment, the parallel light beam that has passed through the light beam passage space 308 has its optical path bent in the + Z direction by the three-wavelength raising mirror 206, is incident on the second objective lens 207, and is collected. A light spot is irradiated onto a track on an information recording surface of a recording medium (DVD).

  The light beam reflected by the track on the information recording surface passes through the second objective lens 207 and becomes a parallel light beam as in the first embodiment, and is reflected by the three-wavelength rising mirror 206 and passes through the light beam passage space 307. -Pass in the X direction. This parallel light beam is converted into S-polarized light by the three-wavelength quarter-wave plate 609, passes through the three-wavelength liquid crystal aberration correction element 608, passes through the fourth collimating lens 903, and becomes a convergent light beam. The light passes through the wavelength prism 902. Thereafter, the light is substantially totally reflected by the reflecting surface of the dichroic prism 906 and is incident on a light detection unit (not shown) of the DVD hologram unit which is the first hologram unit 905.

  Next, the CD optical system will be described. Reference numeral 907 denotes a CD hologram unit which is a second hologram unit, and a linearly polarized divergent light beam (P-polarized light) having a wavelength λ3 = 780 nm band is emitted from a laser light emitting unit (not shown), and a CD auxiliary lens 908 and a dichroic prism. 906 is transmitted. Thereafter, the light passes through the third three-wavelength prism 902, passes through the fourth collimating lens 903, and is converted into a parallel light beam. In this embodiment, the CD auxiliary lens 908 and the fourth collimating lens 903 set the optical magnification of the CD optical system to about 4 times. Thereafter, the light enters the three-wavelength liquid crystal aberration correction element 608, is converted into circularly polarized light by the quarter-wave plate 609 corresponding to the three wavelengths, and passes through the objective lens driving unit 114.

  Similar to the first embodiment, the parallel light beam that has passed through the light beam passage space 308 has its optical path bent in the + Z direction by the three-wavelength raising mirror 206, is incident on the second objective lens 207, and is collected. A light spot is irradiated onto a track on an information recording surface of a recording medium (CD). The light beam reflected by the track on the information recording surface passes through the second objective lens 207 and becomes a parallel light beam as in the first embodiment, and is reflected by the three-wavelength rising mirror 206 and passes through the light beam passage space 307. -Pass in the X direction. This parallel light beam is converted into S-polarized light by the three-wavelength quarter-wave plate 609, passes through the three-wavelength liquid crystal aberration correction element 608, passes through the fourth collimating lens 903, and becomes a convergent light beam. The light passes through the wavelength prism 902. Thereafter, the light passes through the dichroic prism 906 and the CD auxiliary lens 908 and enters the light detection unit (not shown) of the CD hologram unit which is the second hologram unit 907. Since the hologram unit is a known technique, description thereof is omitted here.

  In this embodiment, a DVD hologram unit and a CD hologram unit are used, the fourth collimating lens 903 is arranged in the common optical path of the DVD optical system and the CD optical system, and the CD auxiliary lens 908 is arranged in the optical path of only the CD optical system. did. That is, the fourth collimating lens 205 determines the optical magnification of the DVD optical system, and the fourth collimating lens 903 and the CD auxiliary lens 908 determine the optical magnification of the CD optical system. In this embodiment, the optical magnification of the DVD optical system is about 5 to 6 times, the optical magnification of the CD optical system is about 4 times, and the optimum optical magnification can be set for each DVD and CD optical system. There is an effect that the utilization efficiency can be greatly improved.

  In addition, the second objective lens 207, that is, the HD DVD, DVD, and CD compatible objective lens has a diffraction groove on the incident surface in order to make the three media compatible, but the incident light of the DVD and CD is weakened from the parallel state. By changing the design to a divergent or weakly converged state, it is possible to design such that the efficiency with DVD and CD is improved. In the present embodiment, since the DVD optical system and the CD optical system are separate, the above design change can be used, and the light utilization efficiency of the DVD optical system and the CD optical system can be further improved. Further, by using the DVD hologram unit and the CD hologram unit, the DVD optical system, the CD optical system, and the blue-violet laser are on one side with respect to the axis line connecting the rotation center of the information recording medium and the center of the second objective lens 207. Light sources can be arranged together, and the optical system can be prevented from becoming large and complicated.

  So far, an embodiment of an optical pickup corresponding to four types of optical information recording media of BD, HD DVD, DVD, and CD has been described. In this embodiment, an optical information recording / reproducing apparatus equipped with the above optical pickup is described. This embodiment will be described with reference to FIG.

  FIG. 10 shows a schematic block diagram of an information recording / reproducing apparatus 1001 for recording and reproducing information. Reference numeral 1002 denotes an optical pickup according to the present invention, and a signal detected from the optical pickup 1002 is sent to a servo signal generation circuit 1003 and an information signal reproduction circuit 1004 in the signal processing circuit.

  The servo signal generation circuit 1003 generates a focus control signal, a tracking control signal, and a spherical aberration detection signal suitable for the optical disc 1005 from the signal detected by the optical pickup 1002, and based on these signals, the light is transmitted through the objective drive unit circuit 1006. An objective lens actuator (not shown) in the pickup 1002 is driven to control the position of the objective lens 1007. In the servo signal generation circuit 1003, a spherical aberration detection signal is generated from the optical pickup 1002, and a spherical aberration correction optical system (not shown) in the optical pickup 1002 passes through the spherical aberration correction drive circuit 1008 based on this signal. Drive the correction lens.

  The information signal reproduction circuit 1004 reproduces the information signal recorded on the optical disc medium 1005 from the signal detected from the optical pickup 1002 and outputs the information signal to the information signal output terminal 1009. Note that part of the signals obtained by the servo signal generation circuit 1003 and the information signal reproduction circuit 1004 are sent to the system control circuit 1010.

  A laser drive signal is sent from the system control circuit 1010, the laser light source lighting circuit 1011 is driven to control the amount of light emission using a front monitor (not shown), and the optical disc medium 1005 is passed through the optical pickup 1002. Record the signal. Further, the polarization direction conversion element drive circuit 1019 is driven to perform control so that a predetermined voltage is not applied to or applied to a polarization direction conversion element (not shown) in the optical pickup 1002. An access control circuit 1012 and a spindle motor drive circuit 1013 are connected to the system control circuit 1010, and access direction position control of the optical pickup 1002 and rotation control of the spindle motor 1014 of the optical disc 1005 are performed, respectively. When the user controls the information recording / reproducing apparatus 1001, the control is performed by the user instructing the user input processing circuit 1015. At this time, display of the processing state and the like of the information recording / reproducing apparatus is performed by the display processing circuit 1016.

In Example 1, the figure which simplified and showed the BD optical system of this invention In Example 1, the figure which simplified and showed the HD DVD of this invention, DVD, CD optical system FIG. 6 is a diagram illustrating a structure around the objective lens driving unit 114 in the first embodiment. FIG. 6 is a diagram illustrating another example of the rising mirror 112 and the three-wavelength rising mirror 206 in the first embodiment. In Example 1, it is a figure at the time of using another optical path changing optical element. The figure which shows the detail of BD, HD DVD, DVD, the optical pick-up corresponding to CD in Example 1. The figure which shows the example of the optical pick-up corresponding to BD, DVD, CD. The figure which shows BD optical system in Example 2. The figure which shows HD DVD, DVD, CD optical system in Example 2. Schematic block diagram of an information recording / reproducing apparatus for recording and reproducing information in the third embodiment

Explanation of symbols

102 Blue-violet laser light source 103 Polarization direction conversion element 104 Polarization direction separation element 107 Optical path changing optical element 113 First objective lens 114 Objective lens drive unit 117 BD photodetector 203 Second three-wavelength prism 205 Second collimating lens 207 Second objective lens 208 Two-wavelength multi-laser 209 First three-wavelength prism 210 HD DVD / DVD / CD photodetector 308 Light beam passage space 310 provided on yoke 306 Light beam passage space 311 provided on substrate 304 Suspension Light beam passage space 312 provided in the holder 302 Light beam passage space 905 provided in the yoke 306 DVD hologram unit 907 which is the first hologram unit CD hologram unit 1019 which is the second hologram unit Polarization direction conversion element drive circuit

Claims (8)

A laser light source that emits a linearly polarized light beam;
A polarization direction conversion element that converts the polarization direction of the light beam;
A polarization separation optical element that separates the polarization of the light beam emitted from the polarization direction conversion element;
A first objective lens for condensing the light beam transmitted through the polarization separation optical element on the information recording surface of the information recording medium;
A prism for reflecting the light beam reflected by the polarization separation optical element;
A second objective lens that focuses the light beam emitted from the prism on the information recording surface of the information recording medium;
The first objective lens and the second objective lens are held so as to be aligned in a tangential direction of the information recording medium, and the first objective lens and the second objective lens are driven in a predetermined direction. An objective lens drive unit;
An optical path changing optical element having two internal reflection surfaces, the two internal reflection surfaces provided so as to form an angle of approximately 90 degrees with each other,
A first light beam that is transmitted through the polarization separation optical element and whose optical path is changed by the optical path changing optical element, and a second light beam that is reflected from the polarization separation optical element and reflected by the prism are recorded in the information recording medium. An optical pickup in which the objective lens drive unit has a space that allows passage from different directions with respect to the tangential direction of the medium.   2. The optical pickup according to claim 1, wherein the first light beam is incident on the first objective lens and the second light beam is incident on the second objective lens.   2. The optical pickup according to claim 1, wherein the optical path changing optical element is a trapezoidal prism, and the trapezoidal prism is arranged such that the direction of the lower bottom side of the trapezoidal surface is parallel to the radial direction of the information recording medium. An optical pickup characterized by being arranged in   2. The optical pickup according to claim 1, wherein the polarization separation optical element and the prism are arranged side by side in the radial direction of the information recording medium, and the polarization separation optical element is disposed on the outer peripheral side of the information recording medium with respect to the prism. An optical pickup characterized by   2. The optical pickup according to claim 1, further comprising a second laser light source that emits laser light having a wavelength longer than that of the first laser light source when the laser light source is the first laser light source. An optical pickup characterized by that.   2. The optical pickup according to claim 1, wherein a spherical aberration correcting optical element is disposed in an optical path between the prism and the second objective lens.   The optical pickup according to claim 1, further comprising: a first hologram unit that emits a light beam having a wavelength λ2 different from a wavelength λ1 of the light beam of the laser light source and receives the light beam reflected by the information recording medium; An optical pickup comprising: a second hologram unit that emits a light beam having a wavelength λ3 (λ2 <λ3) and receives the light beam reflected by the information recording medium. An optical information recording / reproducing apparatus for recording or reproducing information,
An optical pickup having a laser light source that emits a linearly polarized light beam, and the polarization direction conversion element that converts a polarization direction of the light beam;
A laser driving circuit for driving a laser light source mounted on the optical pickup;
A polarization direction conversion element driving circuit for driving a polarization direction conversion element mounted on the optical pickup,
The optical pickup further comprises:
A polarization separation optical element that separates the polarization of the light beam emitted from the polarization direction conversion element;
A first objective lens that focuses the light beam transmitted through the polarization separation optical element on an information recording surface of the information recording medium;
A prism for reflecting the light beam reflected by the polarization separation optical element;
A second objective lens that focuses the light beam emitted from the prism on the information recording surface of the information recording medium;
Holding the first objective lens and the second objective lens so as to be aligned in a tangential direction of the information recording medium, and driving the first objective lens and the second objective lens in a predetermined direction An objective lens drive unit;
An optical path changing optical element having two internal reflection surfaces, the two internal reflection surfaces provided so as to form an angle of approximately 90 degrees with each other,
A first light beam that is transmitted through the polarization separation optical element and whose optical path is changed by the optical path changing optical element, and a second light beam that is reflected from the polarization separation optical element and reflected by the prism are recorded in the information recording medium. An optical information recording / reproducing apparatus in which a space capable of passing from different directions with respect to a tangential direction of a medium is formed in the objective lens driving unit.

Images